Parts of the DMX-512 protocol were based on (or lifted from) the ColortranCMXsystem, including the use of 5-pin XLR connectors and RS-485 signal levels. The data rates are different (250K bits per second for DMX-512, 156K for CMX). I don't know all the details of CMX, though, and hadn't planned on doing my own converter for it.
Artistic License, a British company, includes CMX as one of the input choices on their protocol converter (also as one of the output choices - they're very egalitarian). I found it with a quick Google on "CMX converter." Also found that CMX is the file extension for a graphics file format and had to go through a couple pages of file-format converters to find the Artistic License unit. There may be others.
This is actually quite an old post from when I was TD at my local community theatre. The dimmers (still in use) are 2x Colortran ENR 96 from 1995. The board was replaced by an ETCExpress a few years before it was discontinued. Turns out, no converter was needed!
The dimmers will need to be replaced eventually. Many of them have "smiling modules" and some of the plastic tabs have broken off the rear of the modules due to swapping (they only installed about 75% of the dimmers and the rest were airflow modules).
They really need to take the dimmers with broken tabs and transplant the guts in to the airflow modules. They recently bought used ENR modules to fill the rack. The tabs I'm speaking of covered the slot which makes contact with the bus bars. Them being cracked or chipped might not be the best situation. I haven't done a show in this space in about three years though, so I'm unsure of their current condition.